The field of the present invention relates to the delivery of energy impulses (and/or fields) to bodily tissues for therapeutic purposes. The invention relates more specifically to devices and methods for treating conditions associated with bronchial constriction, including: asthma, anaphylaxis, chronic obstructive pulmonary disease (COPD), exercise-induced bronchospasm and post-operative bronchospasm. The energy impulses (and/or fields) that are used to treat those conditions comprise electrical and/or electro-magnetic energy, delivered non-invasively to the patient.
The use of electrical stimulation for treatment of medical conditions is well known. For example, electrical stimulation of the brain with implanted electrodes has been approved for use in the treatment of various conditions, including pain and movement disorders such as essential tremor and Parkinson's disease. Another application of electrical stimulation of nerves is the treatment of radiating pain in the lower extremities by stimulating the sacral nerve roots at the bottom of the spinal cord [Paul F. WHITE, Shitong Li and Jen W. Chiu. Electroanalgesia: Its Role in Acute and Chronic Pain Management. Anesth Analg 92 (2001):505-513; U.S. Pat. No. 6,871,099 entitled Fully implantable microstimulator for spinal cord stimulation as a therapy for chronic pain, to Whitehurst, et al].
Another example of electrical stimulation for treatment of medical conditions is vagus nerve stimulation (VNS, also known as vagal nerve stimulation). It was developed initially for the treatment of partial onset epilepsy and was subsequently developed for the treatment of depression and other disorders. The left vagus nerve is ordinarily stimulated at a location within the neck by first surgically implanting an electrode there and then connecting the electrode to an electrical stimulator [U.S. Pat. No. 4,702,254 entitled Neurocybernetic prosthesis, to ZABARA; U.S. Pat. No. 6,341,236 entitled Vagal nerve stimulation techniques for treatment of epileptic seizures, to OSORIO et al; U.S. Pat. No. 5,299,569 entitled Treatment of neuropsychiatric disorders by nerve stimulation, to WERNICKE et al; G. C. ALBERT, C. M. Cook, F. S. Prato, A. W. Thomas. Deep brain stimulation, vagal nerve stimulation and transcranial stimulation: An overview of stimulation parameters and neurotransmitter release. Neuroscience and Biobehavioral Reviews 33 (2009) 1042-1060; GROVES D A, Brown V. J. Vagal nerve stimulation: a review of its applications and potential mechanisms that mediate its clinical effects. Neurosci Biobehav Rev 29 (2005):493-500; Reese TERRY, Jr. Vagus nerve stimulation: a proven therapy for treatment of epilepsy strives to improve efficacy and expand applications. Conf Proc IEEE Eng Med Biol Soc. 2009; 2009:4631-4634; Timothy B. MAPSTONE. Vagus nerve stimulation: current concepts. Neurosurg Focus 25 (3,2008):E9, pp. 1-4; ANDREWS, R. J. Neuromodulation. I. Techniques-deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation. Ann. N.Y. Acad. Sci. 993 (2003): 1-13; LABINER, D. M., Ahern, G. L. Vagus nerve stimulation therapy in depression and epilepsy: therapeutic parameter settings. Acta. Neurol. Scand. 115 (2007): 23-33].
Many such therapeutic applications of electrical stimulation involve the surgical implantation of electrodes within a patient. In contrast, devices used for the medical procedures that are disclosed herein do not involve surgery. Instead, the present devices and methods stimulate nerves by transmitting energy to nerves and tissue non-invasively. A medical procedure is defined as being non-invasive when no break in the skin (or other surface of the body, such as a wound bed) is created through use of the method, and when there is no contact with an internal body cavity beyond a body orifice (e.g., beyond the mouth or beyond the external auditory meatus of the ear). Such non-invasive procedures are distinguished from invasive procedures (including minimally invasive procedures) in that the invasive procedures insert a substance or device into or through the skin (or other surface of the body, such as a wound bed) or into an internal body cavity beyond a body orifice.
For example, transcutaneous electrical stimulation of a nerve is non-invasive because it involves attaching electrodes to the skin, or otherwise stimulating at or beyond the surface of the skin or using a form-fitting conductive garment, without breaking the skin [Thierry KELLER and Andreas Kuhn. Electrodes for transcutaneous (surface) electrical stimulation. Journal of Automatic Control, University of Belgrade 18 (2,2008):35-45; Mark R. PRAUSNITZ. The effects of electric current applied to skin: A review for transdermal drug delivery. Advanced Drug Delivery Reviews 18 (1996) 395-425]. In contrast, percutaneous electrical stimulation of a nerve is minimally invasive because it involves the introduction of an electrode under the skin, via needle-puncture of the skin. In what follows, comparison is sometimes made between the disclosed noninvasive methods, versus comparable invasive methods, for purposes of demonstrating feasibility and/or validation of the noninvasive methods.
Another form of non-invasive electrical stimulation is magnetic stimulation. It involves the induction, by a time-varying magnetic field, of electrical fields and current within tissue, in accordance with Faraday's law of induction. Magnetic stimulation is non-invasive because the magnetic field is produced by passing a time-varying current through a coil positioned outside the body, inducing at a distance an electric field and electric current within electrically conducting bodily tissue. The electrical circuits for magnetic stimulators are generally complex and expensive and use a high current impulse generator that may produce discharge currents of 5,000 amps or more, which is passed through the stimulator coil to produce a magnetic pulse. The principles of electrical nerve stimulation using a magnetic stimulator, along with descriptions of medical applications of magnetic stimulation, are reviewed in: Chris HOVEY and Reza Jalinous, The Guide to Magnetic Stimulation, The Magstim Company Ltd, Spring Gardens, Whitland, Carmarthenshire, SA34 0HR, United Kingdom, 2006. In contrast, the magnetic stimulators that are disclosed herein are relatively simpler devices that use considerably smaller currents within the stimulator coils. Accordingly, they are intended to satisfy the need for simple-to-use and less expensive non-invasive magnetic stimulation devices, for use in treating bronchoconstriction, as well as use in treating other conditions.
Potential advantages of such non-invasive medical methods and devices relative to comparable invasive procedures are as follows. The patient may be more psychologically prepared to experience a procedure that is non-invasive and may therefore be more cooperative, resulting in a better outcome. Non-invasive procedures may avoid damage of biological tissues, such as that due to bleeding, infection, skin or internal organ injury, blood vessel injury, and vein or lung blood clotting. Non-invasive procedures are generally painless and may be performed without the dangers and costs of surgery. They are ordinarily performed even without the need for local anesthesia. Less training may be required for use of non-invasive procedures by medical professionals. In view of the reduced risk ordinarily associated with non-invasive procedures, some such procedures may be suitable for use by the patient or family members at home or by first-responders at home or at a workplace. Furthermore, the cost of non-invasive procedures may be significantly reduced relative to comparable invasive procedures.
In the present application, the non-invasive delivery of energy is intended ultimately to dilate constricted bronchial passages of the lung, by relaxing bronchial smooth muscle and/or inhibit mucous production by the mucous glands. The smooth muscles that line the bronchial passages are controlled by a confluence of vagus and sympathetic nerve fiber plexuses. Spasms of the bronchi during asthma attacks, anaphylactic shock, and other pulmonary disorders can often be directly related to pathological signaling within these plexuses, as described below.
Asthma, and other airway occluding disorders resulting from immune responses and inflammation-mediated bronchoconstriction, affects an estimated eight to thirteen million adults and children in the United States. A significant subclass of asthmatics suffers from severe asthma. An estimated 5,000 persons die every year in the United States as a result of asthma attacks. Up to twenty percent of the populations of some countries are affected by asthma, estimated to be more than a hundred million people worldwide. Asthma's associated morbidity and mortality are rising in most countries despite the increasing use of anti-asthma drugs.
Asthma is characterized as a chronic inflammatory condition of the airways. Typical symptoms are coughing, wheezing, tightness of the chest and shortness of breath. Asthma is a result of increased sensitivity to foreign bodies such as pollen, dust mites and cigarette smoke. The body, in effect, overreacts to the presence of these foreign bodies in the airways. As part of the asthmatic reaction, an increase in mucous production is often triggered, exacerbating airway restriction. Smooth muscle surrounding the airways goes into spasm, resulting in constriction of airways. The airways also become inflamed. Over time, this inflammation can lead to scarring of the airways and a further reduction in airflow. This inflammation leads to the airways becoming more irritable, which may cause an increase in coughing and increased susceptibility to asthma episodes.
In general, there are three mechanisms that may be triggered in acute asthma (and other conditions, such as anaphylaxis, as described below). First, allergens induce smooth muscle bronchoconstriction through Ig-E dependent release of mast cell mediators such as histamines, prostaglandins, and leukotrienes. Second, airway hyper-responsiveness resulting from local and central neural reflex stimulation and by mediators of inflammation can increase bronchoconstriction. A third mechanism may stimulate mucosal thickening and edematous swelling of the bronchial walls through increased microvascular permeability and leakage.
In the case of asthma, it appears that the airway tissue has both (i) a hypersensitivity to an allergen that causes the overproduction of the cytokines that stimulate the cholinergic receptors of the nerves and/or (ii) a baseline high parasympathetic tone or a high ramp-up to a strong parasympathetic tone when confronted with any level of cholinergic cytokine. The combination can be lethal. Anaphylaxis appears to be mediated predominantly by the hypersensitivity to an allergen causing the massive overproduction of cholinergic receptor activating cytokines that overdrive the otherwise normally operating vagus nerve to signal massive constriction of the airways. Drugs such as epinephrine drive heart rate up while also relaxing the bronchial muscles, effecting temporary relief of symptoms from these conditions. Publications cited below show that severing the vagus nerve (an extreme version of reducing the parasympathetic tone) has an effect similar to that of epinephrine on heart rate and bronchial diameter, in that the heart begins to race (tachycardia) and the bronchial passageways dilate.
Asthma is typically managed with inhaled medications that are taken after the onset of symptoms, or by injected and/or oral medications that are taken chronically. The medications typically fall into two categories: those that treat the inflammation, and those that treat the smooth muscle constriction. A first strategy is to provide anti-inflammatory medications, like steroids, to treat the airway tissue, reducing the tendency of the airways to over-release the molecules that mediate the inflammatory process. A second strategy is to provide a smooth muscle relaxant (e.g., an anticholinergic) to reduce the ability of the muscles to constrict. As treatments, anticholinergics improve lung function by modifying neural reflexes and parasympathetic vagal tone. While inferior to beta2-agonists as a primary treatment, inhaled anticholinergics are effective as an adjunct to beta2-agonists and the combination offers an advantage in reducing hospital admissions.
It is sometimes advised that patients rely on anti-inflammatory medications and avoidance of triggers, rather than on the bronchodilators, as their first line of treatment. For some patients, however, these medications, and even the bronchodilators are insufficient to stop the constriction of their bronchial passages. Tragically, more than five thousand people suffocate and die every year as a result of asthma attacks [NHLBI National Asthma Education and Prevention Program. Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma (NIH Publication No. 07-4051, Revised August 2007). pp 1-417. NHLBI Health Information Center, P.O. Box 30105. Bethesda, Md. 20824-0105; Padmaja SUBBARAO, Piush J. Mandhane, Malcolm R. Sears. Asthma: epidemiology, etiology and risk factors. CMAJ 181 (9,2009): E181-E190; Lee MADDOX and David A. Schwartz. The pathophysiology of asthma. Annu. Rev. Med. 53 (2002):477-98; ANDERSON GP. Endotyping asthma: new insights into key pathogenic mechanisms in a complex, heterogeneous disease. Lancet 372 (9643,2008): 1107-1119; CAIRNS C B. Acute asthma exacerbations: phenotypes and management. Clin Chest Med. 27 (1,2006):99-108; RODRIGO G J. Predicting response to therapy in acute asthma. Curr Opin Pulm Med. 15 (1,2009):35-38; Barbara P YAWN. Factors accounting for asthma variability: achieving optimal symptom control for individual patients. Primary Care Respiratory Journal 17 (3,2008): 138-147].
Anaphylaxis ranks among the other airway occluding disorders as the most deadly, claiming many deaths in the United States every year. Anaphylaxis (the most severe form of which is anaphylactic shock) is a severe and rapid systemic allergic reaction to an allergen. Minute amounts of allergens may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of an allergen. Anaphylactic shock usually results in death in minutes if untreated. It is a life-threatening medical emergency because of rapid constriction of the airway, resulting in brain damage through oxygen deprivation.
The triggers for anaphylactic reactions range from foods (nuts and shellfish), to insect stings (bees), to medication (radio contrasts and antibiotics). It is estimated that 1.3 to 13 million people in the United States are allergic to venom associated with insect bites; 27 million are allergic to antibiotics; and 5-8 million suffer food allergies. In addition, anaphylactic shock can be brought on by exercise. Yet all such reactions are mediated by a series of hypersensitivity responses that result in uncontrollable airway occlusion driven by smooth muscle constriction, and dramatic hypotension that leads to shock. Cardiovascular failure, multiple organ ischemia, and asphyxiation are the most dangerous consequences of anaphylaxis.
Anaphylactic shock requires immediate advanced medical care. Current emergency measures include rescue breathing, administration of epinephrine, and/or intubation if possible. Rescue breathing may be hindered by the closing airway but can help if the victim stops breathing on his own. Clinical treatment typically includes administration of antihistamines (which inhibit the effects of histamine at histamine receptors, but which are usually not sufficient in anaphylaxis), and high doses of intravenous corticosteroids. Hypotension is treated with intravenous fluids and sometimes vasoconstrictor drugs. For bronchospasm, bronchodilator drugs such as salbutamol are administered [Phil LIEBERMAN. Epidemiology of anaphylaxis. Current Opinion in Allergy and Clinical Immunology 8 (2008):316-320; Hugh A. SAMPSON et al. Second symposium on the definition and management of anaphylaxis: Summary report—Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium. J Allergy Clin Immunol 117 (2006):391-397; Angela W TANG. A practical guide to anaphylaxis. Am Fam Physician 68 (2003):1325-1332 and 1339-1340].
The number of people who are susceptible to anaphylactic responses is estimated to be more than 40 million in the United States. Given the common mediators of both asthmatic and anaphylactic bronchoconstriction, it is not surprising that asthma sufferers are at higher than average risk for anaphylaxis. Tragically, many of these patients are fully aware of the severity of their condition, but nevertheless die while struggling in vain to manage the attack medically. Many of these fatal incidents occur in hospitals or in ambulances, in the presence of highly trained medical personnel who are powerless to break the cycle of inflammation and bronchoconstriction (and life-threatening hypotension in the case of anaphylaxis) affecting their patient. Unfortunately, prompt medical attention for anaphylactic shock and asthma are not always available. For example, epinephrine is not always available for immediate injection. Even in cases where medication and attention is available, life-saving measures are often frustrated because of the nature of the symptoms. Constriction of the airways frustrates resuscitation efforts, and intubation may be impossible because of swelling of tissues. Typically, the severity and rapid onset of anaphylactic reactions does not render the pathology amenable to chronic treatment, but requires more immediately acting medications. Epinephrine is among the most popular medications for treating anaphylaxis, commonly marketed in so-called “Epipen” formulations and administering devices, which potential sufferers carry with them at all times. In addition to serving as an extreme bronchodilator, epinephrine raises the patient's heart rate dramatically in order to offset the hypotension that accompanies many reactions. This cardiovascular stress can result in tachycardia, heart attacks and strokes.
Chronic obstructive pulmonary disease (COPD) is a major cause of disability and is the fourth leading cause of death in the United States. More than 12 million people are currently diagnosed with COPD. An additional 12 million likely have the disease but are unaware of their condition. COPD is a progressive disease that makes it increasingly difficult for the patient to breathe. COPD can cause coughing that produces large amounts of mucus, wheezing, shortness of breath, chest tightness and other symptoms. Cigarette smoking is the leading cause of COPD, although long term exposure to other lung irritants, such as air pollution, chemical fumes or dust may also contribute to COPD. In COPD, there is abnormally low air flow within the bronchial airways for a variety of reasons, including loss of elasticity in the airways and/or air sacs, inflammation and/or destruction of the walls between many of the air sacs and overproduction of mucus within the airways.
The term COPD includes two primary conditions: emphysema and chronic obstructive bronchitis. In emphysema, the walls between many of the air sacs are damaged, causing them to lose their shape and become floppy. This damage can also destroy the walls of the air sacs, leading to fewer and larger air sacs instead of many small ones. In chronic obstructive bronchitis, the patient suffers from permanently irritated and inflamed bronchial tissue that is slowly and progressively dying. This causes the lining to thicken and form thick mucus, making it difficult to breathe. Many of these patients also experience periodic episodes of acute airway reactivity (i.e., acute exacerbations), wherein the smooth muscle surrounding the airways goes into spasm, resulting in further constriction and inflammation of the airways. Acute exacerbations occur, on average, between two and three times a year in patients with moderate to severe COPD and are the most common cause of hospitalization in these patients, with mortality rates of approximately 11%. Frequent acute exacerbations of COPD cause lung function to deteriorate quickly, and patients never recover to the condition they were in before the last exacerbation. As with asthma, current medical management of these acute exacerbations is often insufficient [Dick D. BRIGGS Jr. Chronic obstructive pulmonary disease overview: prevalence, pathogenesis, and treatment. J Manag Care Pharm 10 (4 suppl S-a, 2004):S3-S10; Marc DECRAMER, Wim Janssens, Marc Miravitlles. Chronic obstructive pulmonary disease. Lancet 379 (2012): 1341-1351].
Exercise-induced bronchospasm (EIB) results from a transient increase in airway resistance that occurs five to ten minutes after initiation of exercise. It produces symptoms such as shortness of breath, cough, wheezing, chest tightness, or pain. Eighty to ninety percent of patients with asthma also have EIB, but up to a quarter of non-asthmatic athletes may also experience EIB. The condition is usually treated with short-acting bronchodilator medication, with or without the addition of anti-inflammatory agents, taken 15 to 30 minutes before initiation of exercise. However, many patients do not respond to those treatments, or they experience unwanted side effects. Accordingly, one objective of the present invention is to provide an alternative to pharmacological treatment, through the use of noninvasive vagal nerve stimulation before and/or after exercise [Taru SINHA and Alan K. David. Recognition and management of exercise-induced bronchospasm. Am Fam Physician 67 (2003):769-774].
Bronchospasm is one of the most significant respiratory complications that can occur during surgical anesthesia, and asthmatic patients, as well as some patients with COPD, are at elevated risk for it. Because the beneficial effects of steroids on airway reactivity occurs over a period of hours, patients at risk of experiencing bronchospasm during surgery are sometimes treated with steroids starting 24-48 h before surgery. The patients who are actually wheezing before surgery also receive treatment with inhaled beta-2 adrenergic agents and corticosteroids. Such wheezing may also be experienced by patients without pre-existing reactive airway disease, due to pulmonary edema, pneumothorax, drug reactions, aspiration, and endobronchial intubation. If the pharmacological treatment does not stop or prevent the wheezing, the surgery may be deferred, but this is not always practical or possible in view of the need for surgery. Accordingly, one objective of the present invention is to provide an alternative to pharmacological treatment, through the use of noninvasive vagal nerve stimulation before surgery.
Despite precautions and pre-treatments, bronchospasm may nevertheless occur during surgery, in which case, beta-2 adrenergic agents may also be administered through an endotracheal tube. For some patients, those agents may not be effective or are otherwise contraindicated, and the bronchospasm may continue even after the surgery is completed. Accordingly, another objective of the present invention is to provide an alternative to pharmacological treatment for bronchospasm that occurs during and after surgery, through the use of noninvasive vagus nerve stimulation [Peter ROCK and Preston B. Rich. Postoperative pulmonary complications. Current Opinion in Anaesthesiology 16 (2003): 123-132].
Unlike cardiac arrhythmias, which can be treated chronically with pacemaker technology, or in emergent situations with defibrillators (implantable and external), there is no commercially available medical equipment that can chronically reduce the baseline sensitivity of the smooth muscle tissue in the airways, to reduce the predisposition to asthma attacks, to reduce the symptoms of COPD or to break the cycle of bronchial constriction associated with an acute asthma attack or anaphylaxis. Therefore, there is a need in the art for new products and methods for treating the immediate symptoms of bronchial constriction resulting from pathologies such as anaphylactic shock, asthma, COPD, exercise-induced bronchospasm, and post-operative bronchospasm. In particular, there is a need in the art for non-invasive devices and methods to treat the immediate symptoms of bronchial constriction.
Although energy has been applied previously to patients in such a way as to bring about bronchodilation, those investigations involve methods that are invasive. For example, U.S. Pat. No. 7,740,017, entitled Method for treating an asthma attack, to DANEK et al., discloses an invasive method for directing radio frequency energy to the lungs to bring about bronchodilation. U.S. Pat. No. 7,264,002, entitled Methods of treating reversible obstructive pulmonary disease, to DANEK et al., discloses methods of treating an asthmatic lung invasively, by advancing a treatment device into the lung and applying energy. Those invasive methods attempt to dilate the bronchi directly, rather than to stimulate nerve fibers that in turn bring about bronchodilation.
In contrast, the present invention discloses the use of noninvasive electrical stimulation of the vagus nerve (VNS) to dilate constricted bronchi. U.S. Pat. No. 6,198,970, entitled Method and apparatus for treating oropharyngeal respiratory and oral motor neuromuscular disorders with electrical stimulation, to FREED et al., describes noninvasive electrical stimulation methods for the treatment of asthma and COPD, but they involve direct stimulation of muscles instead of the vagus nerve. The present invention is unexpected because previous reports teach away from the use of (invasive or noninvasive) VNS to treat bronchoconstriction. Thus, in most subjects with asthma, vagal nerve activity contributes in varying degree to bronchoconstriction [OKAYAMA M, Yafuso N, Nogami H, et al. A new method of inhalation challenge with propranolol: comparison with methacholine-induced bronchoconstriction and role of vagal nerve activity. J Allergy Clin Immunol. 80 (1987):291-9]. In fact, a clinical report suggests that vagal nerve stimulation may cause bronchoconstriction [BIJWADIA J S, Hoch R C, Dexter D D. Identification and treatment of bronchoconstriction induced by a vagus nerve stimulator employed for management of seizure disorder. Chest 127 (1,2005):401-402]. Yet other reports list dyspnea or shortness of breath as common side effects of VNS, which is contrary to the objectives of the present invention [MORRIS GL 3rd, Mueller W M. Long-term treatment with vagus nerve stimulation in patients with refractory epilepsy. The Vagus Nerve Stimulation Study Group E01-E05. Neurology 53 (1999):1731-5; Su Jeong YOU, Hoon-Chul Kang, Heung Dong Kim, Tae-Sung Ko, Deok-Soo Kim, Yong Soon Hwang, Dong Suk Kim, Jung-Kyo Lee, Sang Keun Park. Vagus nerve stimulation in intractable childhood epilepsy: a Korean multicenter experience. J Korean Med Sci 22 (2007):442-445; RUSH A J, Sackeim H A, Marangell L B, et al. Effects of 12 months of vagus nerve stimulation in treatment-resistant depression: a naturalistic study. Biol Psychiatry 58 (2005):355-363]. These clinical reports that VNS produces symptoms of bronchoconstriction may be understood from animal experiments that also teach away from the use of VNS to treat bronchoconstriction [BLABER L C, Fryer A D, Maclagan J. Neuronal muscarinic receptors attenuate vagally-induced contraction of feline bronchial smooth muscle. Br J Pharmacol 86 (1985):723-728].
The vagus nerve innervates the heart, which raises additional concerns that even if VNS could be used to dilate bronchi, such vagus nerve stimulation could trigger cardiac or circulatory problems, including bradycardia, hypotension, and arrhythmia, particularly if the right vagus nerve is stimulated [SPUCK S, Tronnier V, Orosz I, Schonweiler R, Sepehrnia A, Nowak G, Sperner J. Operative and technical complications of vagus nerve stimulator implantation. Neurosurgery 67 (2 Suppl Operative, 2010):489-494; SPUCK S, Nowak G, Renneberg A, Tronnier V, Sperner J. Right-sided vagus nerve stimulation in humans: an effective therapy? Epilepsy Res 82 (2008):232-234; THOMPSON G W, Levett J M, Miller S M, Hill M R, Meffert W G, Kolata R J, Clem M F, Murphy D A, Armour J A. Bradycardia induced by intravascular versus direct stimulation of the vagus nerve. Ann Thorac Surg 65 (3,1998):637-42; SRINIVASAN B, Awasthi A. Transient atrial fibrillation after the implantation of a vagus nerve stimulator. Epilepsia 45 (12,2004):1645]. In fact, vasovagal reactions are classically brought about by a triggering stimulus to the vagus nerve, resulting in simultaneous enhancement of parasympathetic nervous system (vagal) tone and withdrawal of sympathetic nervous system tone.
Accordingly, we performed experiments, which are described herein, showing first that invasive electrical stimulation of the vagus nerve can in fact produce bronchodilation without first producing bronchoconstriction [Thomas J. HOFFMANN, Steven Mendez, Peter Staats, Charles W. Emala, Puyun Guo. Inhibition of Histamine-Induced Bronchoconstriction in Guinea Pig and Swine by Pulsed Electrical Vagus Nerve Stimulation. Neuromodulation 12 (4,2009): 261-269]. The success of those and subsequent experiments motivated the present disclosure that noninvasive methods and devices can also produce bronchodilation in humans, provided that the disclosed special devices and stimulation methods are used. Those devices and methods address not only the problems of producing bronchodilation and avoiding the production of abnormal heart rate or blood pressure, but also the problem of stimulating at the skin of the patient in such a way that a vagus nerve is selectively modulated, and in such a way that side effects including muscle twitching and stimulation pain are minimized or avoided.